In a conventional sensor network, a sensor node randomly repeats a dormant state and an active state by automatically going into a dormant state. The method does not reflect characteristics of each sensor network and uniformly applied to an entire sensor network. For example, sensor nodes are usually densely distributed in a place where the sensor nodes are crowded. When required quantities of the sensor data are changed according to a time, a day and a season, the method is uniformly applied. This causes unnecessary battery consumption of the sensor node.
When the Personal Area Network (PAN) coordinator or the cluster head can manage dormancy of the sensor node, this problem is solved. However, it is required to figure out distance information and location information of the sensor node to manage the dormancy of the PAN coordinator or the cluster head. When Global Positioning System (GPS) is not used, the distance information and the location information of the sensor node can be acquired through a Received Signal Strength Indication (RSSI) value and a Triangle of a reception packet. Herein, it is the key to improve the accuracy. The accuracy of the method for acquiring a distance from the sensor node based on the RSSI reception level value has been remarkably improved. An IEEE 802.15.4a standardization group is performing standardization related to grasp of the location of the sensor node. When the distance and the location from the PAN coordinator or the cluster head to the sensor node are accurately acquired, the dormant nodes managing method provided by the present invention can efficiently reduce battery consumption of the sensor node. The more accurate the distance information and the location information of the sensor node are, the more efficient the method is.
According to the IEEE 802.15.4 standard, which is one of standards of the sensor network, a new beacon per 16 slots is transmitted in case that the beacon is used. A period that the beacon is divided by a cycle is called a super frame. The super frame is divided into an active section and an inactive section. Data communication is performed in the active section, but not performed in the inactive section. The sensor nodes take a rest for the inactive section and perform data communication again for the active section. An entire length of the super frame section is about 30 ms. Accordingly, when the sensor node wakes up after taking a rest for the inactive section, the sensor nodes consume battery a lot. Also, since a post beacon section currently exists in the IEEE 802.15.4b standard, a method for preventing a collision between a beacon transmitted from the PAN coordinator and a beacon transmitted from the cluster header is provided.
As described above, since the methods do not reflect characteristics of each sensor network and are uniformly applied to the entire sensor network, there is a problem that the battery is unnecessarily consumed.
Therefore, a method for reducing battery consumption of the sensor nodes and efficiently maintaining a network is essentially required.